Thecus iSCSI NAS servers allow users to create iSCSI target volumes, whenever the need arises to expand storage capacity, up to 5 Thecus NAS devices can be stacked together using the built-in iSCSI initiator.
These can be stacked through single network access like SMB or AFP acting as a share folder type.

1.When the customer sets up stackable mode, this must be in iSCSI mode, is this right? Can stack up to 5 boxes is this right?

Ans: The host NAS could connect up to five Thecus NAS boxes via iSCSI protocol.

2.Is there a total capacity limit when used in stack mode?

Ans: The old stackable guide, http://www.thecus.com/download/manual/Stackable_V11_EN.pdf , indicates 20 TB. It was talking about installing 1 TB drive in five N5200PRO though. Please read new stackable guide, http://www.thecus.com/download/howtoguide/HowtoStackThecusNAS.pdf , currently we have 2TB single drive and N8800, so the overall capacity could be doubled to 40 TB and even more.

3.When you stack all 5 units together, does this show as one network share with the total capacity of all 5 boxes?

Ans: In short, an iSCSI volume on the target NAS could be mounted as a share folder on the host NAS. It means the folder capacity is bounded to the iSCSI volume size. A client computer could reach the host NAS via IP or host name, and then many share folders could be found, some are in host NAS and the other are from target NAS boxes.

4.If one box was to fail what would happen to the network share? Would if fail? Would any data still be accessible? If so, how?

Ans: In case target NAS #3 failed, NAS admin could receive email notification or other alarms, if they are correctly set and configured in advance. However, for client computers, they just found some share folders failed to access.